"He's played the best over the past couple of months. The way I like to see the rankings work is the guy who is winning the most tournaments should be the number-one player."

Scott said while he has been consistent this season, he is frustrated at only winning one event to McIlroy's three, but he plans on upping the ante at Valhalla.

"I hope that I could go ahead and win this week and maybe go back to number one," he said.

Away from who will be number one after this weekend, the big question at Valhalla is whether former number one Tigers Woods will take part.

While his image is displayed on the promotional banners, Woods is yet to be seen at the host club as he remains in Florida receiving treatment for the back injury he suffered on Sunday in the WGC event - where he withdrew after the ninth hole.

Woods has played only nine complete rounds since undergoing back surgery in March to ease a pinched nerve, and had his worst 72-hole showing at a major at the British Open with a share of 69th.

Day fancies chances at PGA Championship

Jason Day has recovered from an episode of vertigo and hopes to be a dark horse at the PGA Championship.

While admitting he is not yet at the peak of his golfing powers in an injury- and illness-affected season, Day believes the style of course and a lack of expectation from others could spur him to something big.

The world number nine struggled with his left thumb and wrist injury during the recent British Open and withdrew from last week's WGC event with vertigo, likely a side effect of drugs used to combat a sixth bout of strep throat for 2014.

I feel a lot more comfortable and confident than I felt going into last week ... I am feeling great.

Jason Day

Having not been at 100 per cent since suffering the thumb complaint when winning the WGC Match Play in late February, Day was much more upbeat after some good practice at Valhalla.

"I feel a lot more comfortable and confident than I felt going into last week because I get a lot of my confidence from how I am hitting the ball and given the last few days' work I have put in, I am feeling great," Day said.

"I haven't had any dramas since the initial bout of vertigo so that's great."

The Queenslander has been forced to temper his expectations for most of the year but has still knocked out some decent results, most noticeably a fourth-place finish at the US Open.

He also showed some spark in Tuesday's practice round by booming a tee ball 338 yards in the championship's long-drive competition, leading the event until late when South African Louis Oosthuizen put one 340 yards out.